The present invention relates to precision coil structures and methods for winding such structures and, in particular, to an improved configuration for deflection coils in magnetic deflection yokes and a method for winding a precisely defined magnetic deflection yoke.
Deflection coils for electron beams normally include longitudinal portions, radial portions, and transverse portions. The longitudinal portions are generally along the axis of the electron beam device such as a cathode ray tube. Current through the longitudinal portions produces a component of magnetic field that is transverse to the axis of the beam which causes a deflection of the beam. Current flowing through the radial portions and the transverse portions of deflection coils produce components of magnetic field axially directed which tends to defocus the electron beam.
A usual production technique in the manufacture of magnetic deflection yokes is to wind the coils on a bobbin device separate from the yoke core and then fit the coils onto the core. As a result, it is difficult or impossible to achieve precision or predictability as to placement or distribution of either the longitudinal portions, the radial portions or the transverse portions of each coil or group of coils. Hence, such magnetic deflection yokes do not have predictable magnetic field patterns.
Imprecision in the deflection coils results in various distortions when an image is displayed on the face of a cathode ray tube. One is the defocusing of the spot and changes in its shape at positions away from the center of the CRT, and another is the lack of perpendicularity between the x and y components due to the imprecise placement of the x and y deflection coils with respect to each other.
Prior art attempts to correct the distortions due to imprecise placement and distribution of deflection coils have included very high cost methods requiring manual winding and forming of deflection coils.
Accordingly, it is an object of the present invention to wind deflection coils which will produce predictable magnetic fields.
A further object is to wind deflection coils on an internally slotted core structure with end caps arranged to achieve a high degree of repeatability among a large number of coils produced.
A still further object of the present invention is to reduce defocusing and distortion due to end effects of the magnetic deflection coils.
Other objects of the invention are to provide, in an improved deflection yoke as aforesaid, a core structure on which the coils are wound in their final position, and which provides desired lineal response in the operation of the yoke.
Another object of the present invention is to provide a low cost magnetic deflection yoke which will produce a predictable magnetic field for deflecting an electron beam.